Distribution of in utero and ETS exposure among participants in the Children's Health Study, 1993 (n = 3357)
| No. (%) | |
| Exposure | |
| In utero | 620 (19) |
| Any past or current ETS household exposure | 1325 (42) |
| Current household smokers | |
| Mother | 435 (13) |
| Father | 405 (12) |
| Other | 174 (5) |
| Number of current household smokers | |
| 0 | 2509 (77) |
| 1 | 482 (15) |
| 2+ | 266 (8) |
| Number of cigarettes/day | |
| 0 | 2349 (75) |
| 1–9 | 366 (12) |
| 10+ | 415 (13) |
| Past ETS household exposure | |
| Mother | 576 (18) |
| Father | 645 (20) |
| Other | 174 (5) |
| In utero and any past or current ETS household exposure | |
| No in utero and no ETS | 1756 (56) |
| Only ETS | 759 (24) |
| In utero and no ETS | 82 (3) |
| In utero and ETS | 527 (17) |
ETS = environmental tobacco smoke.